How often do we need calories? Would one 8000 calorie meal every four days replace four 2000 calorie meals every day? Is four 500 calorie meals a day better than one 2000 calorie meal a day?

Question

I was wondering this the other day. It’s similar I think to “How efficient is out digestive system”. Is there an optimal number of calories to take in every X amount of time to maintain a steady…calorie intake? Energy generation?

In: Biology

Answer 1

So just starting with some basics on how much energy you have available within body at all time. Average body fat is 18–24% in man and 25-31% in woman ([Average body fat](https://en.wikipedia.org/wiki/Body_fat_percentage#Typical_body_fat_amounts)). Average US man is 69.0 inches (5ft 9in, ) tall and weights 197.8 pounds, for women it is 63.6 in, 170.5 pounds ([Average body measurements](https://www.cdc.gov/nchs/fastats/body-measurements.htm)).

When you put these measurements into TDE (total daily expenditure) calorie calculator (e.g. this [one](https://tdeecalculator.net/)), you’ll get for 25 year old male with these measurements, 20% of body fat and sedentary office job 2297 calories per day. 1914 calories of that is BMR (basal metabolic rate). These are the calories the body will need no matter what, just to keep lights on.

20% of 197.8 is 39.56 pounds of fat, which at 3500 calories per pound gives you 138,460 stored calories. At calculated TDE this is enough for 60 days.

You have also some glucose stored in form of glycogen in your muscle and liver. The amount of glycogen stores depends on many things, like your training status, metabolic balance and eating, but on average you have about 100g in liver and additional 400g in skeletal muscle. At 4 cal per g, that gives you ~2000 cal stored as carbohydrate. Muscle glycogen can be only used directly in the muscle and not transported out, while liver glycogen serves to balance glucose amount in the blood.

The final macro-nutrient, protein and its building blocks amino acids do not have any storage mechanisms as such, they are just present in all cells and obviously a lot of total amount is again in skeletal muscle.

So finally to your question. 8000 calories every 4 days would be enough to replenish the calories, but more than likely wouldn’t be optimal eating strategy. Disregarding the problem of just digesting all that food, which our digestive tract can do, but will probably have some problems with, you will run out of stored glycogen needed to keep stable blood glucose level.

Your body will switch to “backup system” of feeding your brain with ketones, generated from fat. This will happen generally in about 2-3 days, and is not that pleasant if you are not used to this. Then your eat your huge meal on day 4, switch back to glucose, inducing probably huge insulin spikes. Not at all healthy.
If you were on high fat ketogenic diet, you would probably avoid this problem, but would still face trouble of loading your digestive system with a lot of fat and protein every 4 days.

You will also have problems for example with training/demanding physical activity. You’ll break down some muscle and need to replace it. Now you didn’t eat for 3 days and your circulating amino acid levels are low. Your body has to take them from some other part of the body, e.g. you train your biceps and amino acids will be provided by your leg muscles. Next day you go for your leg day and amino acids will be taken from you pecs. Pointless. Then you eat your 8000 calories, including a lot of protein. But there is no way to store amino acids outside of the muscle and muscle won’t be build that fast. So most of the amino acids will be just burned as fuel or deaminated and converted to stored glycogen/fat.

Now 4x 500 calorie meals a day – probably OK, it was preferred strategy by bodybuilders for long (sometime going to 6 meals/snacks or more), exactly because they were afraid of running out of readily available amino acids for muscle building. But each meal, if it contains sugars, will also spike your insulin and there are some indications it’s not the healthiest thing to do.

Finally one meal a day – if your digestive tract can handle it, this should be OK. Some people prefer doing OMAD (One Meal a Day). You provide your body with some potential benefits of intermittent fasting, such as low and stable insulin level, some autophagy activation and also if you time it right, it should support your natural circadian rhythms and improve your sleep. Digesting such large meal still takes some time and amino acids will be released from digested protein over several hours.

What is absolutely best way to distribute your calories in time is not completely clear and it might differ based on what you want to optimize for (general health and longevity, maximum athletic performance), but probably is somewhere in that range of 1-4 meals per day, with maybe some longer fast from time to time.